1. Field of the Invention
The present invention relates generally to power converters, and, more specifically, the present invention relates to transformerless, multi-level power converter utilizing existing generators in ship-board propulsion applications.
2. Description of the Background
The cascaded, multi-level inverter can be adapted to a variety of different applications covering a wide range of industries. This voltage source topology is advantageous compared to other topologies because of its straightforward implementation and flexibility. The cascaded, multi-level inverter can be tailored to match available input voltage levels while providing a flexible arrangement in order to obtain a required output voltage level with known harmonic distortion characteristics.
The traditional implementation of a cascaded, multi-level inverter requires the use of a dc voltage source that can be either a single source with multiple series-connected voltage levels that share a common ground connection, or multiple, isolated dc power sources. These dc voltages are typically derived from isolated transformer secondary windings connected to rectifier circuits. The size and weight of the transformer are affected by the number of isolated windings and the required power level. The number of isolated secondary windings can be significant when applied to a multi-phase, multi-level power converter. The use of these transformers is less than ideal as they add complexity and cost to the voltage source topology.
As such, there is a need in the art to provide improved cascaded, multi-level topologies that address one or more of the above-described and other limitations to prior art systems. The present invention specifically addresses a system configuration consisting of a cascaded, multi-level inverter, or a variant referred to as the multi-source, flying source inverter, whose ac input voltage is derived from an electromagnetic generator.